The present invention relates to a rotor of a magneto and the like to be used for ignition equipment of an internal combustion engine and more particularly to a rotor the core of which has a metal hub to be used for fitting a rotating axis such as a crankshaft.
Prior Art
The conventional rotor of rotating equipment such as a magneto consists of a rotor core incorporating a pole piece portion holding a magnet and a balance weight portion, into which a hub is integrated as well. Also, said rotor is so constructed that, by injecting melt aluminum into a die wherein said rotor core is set, said hub made from an aluminum die cast which is used to connect a rotating axis such as a crankshaft is integrally molded into said rotor core.
Such a rotor equipped with a hub made of an aluminum die cast has a tapered axis hole portion to ensure easy and firm attachment of a rotating axis such as a crankshaft to said hub. The length of the taper axis hole in relation to thickness of the laminated rotor core and/or the position in the axial direction are arbitrarily set so that desired strength is obtained. Moreover, as said hub is made of an aluminum die cast, the hub can be provided with a faucet joint portion at its the circumference area through a cutting process to attach a cooling fan or a screw hole is formed to be used for attaching various parts such as a ratchet nail for recoiling. Therefore, this hub is capable of enough firmly supporting such a heavy cooling fan or ratchet nails which receive a large load stress. However, because such a conventional rotor of rotating equipment comprises laminated cores and aluminum die cast products in an integrated form and furthermore aluminum casting for the hub is carried out with a magnet being inserted into the pole piece portion, the rotor core, when the hub is molded, is made heavier in weight and molding of the hub becomes troublesome, as a result, causing less productivity and high casting cost. Additionally, there has been a problem that, due to a decrease in magnetic property of said magnet caused by heat generated through casting process of the hub, a process of magnetization of the magnet is required again after the aluminum die casting, resulting in a large increase in product costs. On the other hand, in recent years, there have emerged needs of users for large reduction in product costs and achievement of the light weight and, therefore, molding of a hub to be used for a rotor core has been attempted using synthetic resins instead of aluminum die casts. There has been, however, another problem that such synthetic resins are useless when the strength in supporting a rotating axis is to be obtained by lengthening said tapered axis hole more than the laminated layer of the rotor core and by deviating the position of said tapered axis hole in the direction of the axis. In addition, if screwing processing for fitting various heavy parts is given to such synthetic resins or attachment of the faucet joint portion to which a cooling fan and the like are fitted thereto, it causes a problem in terms of strength in the same way as described above and it is not realistic as well.